1. Field of the Invention
The present invention relates to a display device in thin film form and a method for production thereof. More particularly, the present invention relates to a new display device including a transparent conductive film and an aluminum alloy film as constituents, which are used for flat panel displays (such as liquid crystal display) of active or passive matrix type, reflecting film, and optical parts, and a method for production thereof.
2. Description of the Related Art
A liquid crystal display device of active matrix type is composed of two mutually opposing substrates and a liquid crystal layer held between them. It relies on thin film transistors (TFT) as switching devices. The first substrate has a transparent conductive film and an array of TFTs connected to scanning lines and signal lines. The second substrate, which is a certain distance away from the first one, has a common electrode. By contrast, a liquid crystal display device of passive matrix type is also composed of two mutually opposing substrates and a liquid crystal layer held between them. The first substrate for wiring has scanning lines and signal lines. The second substrate, which is a certain distance away from the first one, has a common electrode. The transparent conductive film is formed from indium tin oxide (ITO) which is indium oxide (In2O3) doped with about 10 wt % of tin oxide (SnO).
The signal lines are formed from pure aluminum or aluminum alloy (such as Al—Nd), and they are electrically connected to the transparent conductive film via refractory barrier metal such as Mo, Cr, Ti, and W. However, omission of barrier metal for direct connection of the signal lines to the transparent conductive film is now under study.
It is shown in Patent Document 1 that direct contact between signal lines and transparent conductive film is possible if the latter is formed form IZO (indium oxide doped with about 10 wt % of zinc oxide).
It has been confirmed that contact resistance between the signal lines and the transparent conductive film can be kept low even though the above-mentioned refractory metal is omitted so long as the drain electrode undergoes surface treatment by exposure to plasma or by ion implantation (as disclosed in Patent Document 2) or the gate, source, and drain electrodes have two-layered structure, with the second layer containing an impurity such as N, O, Si, and C (as disclosed in Patent Document 3).
Patent Document 1:
Japanese Patent Laid-open No. Hei-11-337976
Patent Document 2:
Japanese Patent Laid-open No. Hei-11-283934
Patent Document 3:
Japanese Patent Laid-open No. Hei-11-284195